Effect of cyclic irrigation using moderately saline and non‐saline water on onion (Allium cepa L.) yield and soil salinization in semi‐arid areas of Northern Ethiopia*

Abstract

Due to the scarcity and/or unreliability of canal water supply, seepage water is haphazardly used for sole irrigation or in conjunction with canal water in most small-scale irrigation schemes in northern Ethiopia. This has been a major cause of low crop yield and has aggravated soil salinization. The problem is more exacerbated for onion, which is the major irrigated vegetable crop and is sensitive to salinity. Thus, it is essential to assess a sustainable way to use both water resources conjunctively for the production of onion. A new study in the Ethiopian context was conducted to evaluate the effect of cyclic irrigation using non-saline canal water (EC, 0.41-0.78 dS m −1) and moderately saline seepage water (EC, 0.82-2.19 dS m −1) on onion yield and soil salinization for two seasons (2014/2015 and 2015/2016) in the Gumselassa irrigation scheme, Ethiopia. Four irrigation water treatments were applied with three replications consisting of: C (canal), S (seepage), 2CS (two canal and seepage) and CS (canal and seepage). In both seasons, the onion bulb yield variations between the C, 2CS and CS treatments were not significant; however, the S treatment reduced the onion yield significantly compared to all but CS in 2015/2016. The S treatment resulted in significant salt accumulation in the upper soil profile (0-20 cm). The alternate (C : S) cyclic option is thus recommended for alleviation of the problem of freshwater scarcity, without undue onion yield reduction and soil salinization in Gumselassa and similar irrigation schemes.

Assessment of Morphological and Biochemical Response of Different Onion Cultivars Under Salt Stress Conditions

“…The attributes such as seed germination (%) and germination intensity decrease by increasing levels of salinity, as salinity and germination have antagonistic response (Baba et al, 2010 and. These results confirmed with findings of Yohannes et al (2020), who reported that increasing levels of salinity stops the plant growth hence decreasing the plant height.…”

“…The increasing level of salinity reduces fresh and dry mass of leaves and plants. Furthermore, lesser number of leaves were also observed with increasing levels of salinity (Yohannes et al, 2020). This is might be due to the absorbance of less water due to plant tolerance mechanism activity.…”

“…Higher level of salts affects the plant growth that ultimately resists the transfusion of water and nutrient from the soil. Limited supply of nutrients and minerals with effect of salinity stop the plant growth in response where significant decrease in bulbs weight was observed (Yohannes et al, 2020). Moreover, interaction between cultivars and salinity levels was significant and all the varieties showed same response at higher level of salinity.…”

“…The results are confirmed by the international reports of increasing levels of NaCl salt stress decreased growth and total chlorophyll contents in various onion cultivars (Hansi et al, 2016). Fresh and dry weight of onion bulbs reduce due to the effect of higher salt levels of both soil and water (Yohannes et al, 2020). Higher level of salts affects the plant growth that ultimately resists the transfusion of water and nutrient from the soil.…”